Anode set assembly with micro-expanded metal mesh porous transport layer (PTL) for proton exchange membrane (PEM) electrolysis cells and method of making same

Abstract

A PEM electrolyzer PTL (16) is created from micro-expanded mesh metal foil layers to allow for precise level control of the thickness, porosity, tortuosity, pore size, inter-layer connectivity, and surface roughness of these layers. The pore size ranges from 3 m to 30 m, and the porosity (mesh opening area) ranges from 10% to 50%. A PEM anode pack assembly (10) is formed from a micro-expanded PTL layer and a multi-layer expanded metal flow field and bipolar plate. The three sub-components are diffusion bonded together to form an integrated group and PVD coated on the outer surfaces.

Description

Background Technology

[0001] This disclosure relates generally to proton exchange membrane (PEM) hydrogen electrolyzer devices, and more specifically to a novel anode assembly comprising a porous transport layer (PTL) formed of a stack of multilayer diffusely bonded micro-expanded metal meshes.

[0002] A PEM electrolyzer consists of one or more stacked cell units. Each cell unit comprises an anode bipolar plate, an anode-side flow field, an anode PTL, an anode catalyst layer, a central proton-conducting membrane, a cathode catalyst layer, a cathode PTL, a cathode-side flow field, and a cathode bipolar plate. The stacked units are fixed within an electrolyzer frame having a water inlet and a gas outlet. (See also...) Figure 1 ).

[0003] The operation of a hydrogen electrolyzer is well known in the art, in which water circulates through the stack on each side of the PEM, and electrical energy is applied to each side of the anode and cathode. Water supply on each side flows through a flow field and a PTL to reach the inner catalyst layer, where a chemical reaction occurs across the PEM. The chemical reaction across the PEM causes water molecules to split, producing hydrogen on the cathode side and oxygen on the anode side.

[0004] Catalyst materials are well known in the art and are typically applied to the PEM immediately adjacent to the corresponding PTL layer. The performance of the electrolyzer is highly dependent on the catalyst material and density, the electrical contact (ohmic resistance) of the individual layers, the flow field and the pore size of the PTL, the flow path through each layer, and the flow rate. Optimal pore sizes for PTLs have been reported in the range of 6 µm to 15 µm with porosity exceeding 20%. However, producing materials with these properties is both difficult and expensive.

[0005] In existing technologies, to achieve very small pore sizes in PTLs, anode PTLs are typically made of sintered titanium (Ti) powder, sintered Ti fibers, porous Ti foils, or Ti mesh. The pore sizes of conventional metal meshes are typically between 100 µm and 1 mm. The pore sizes of metal foils (mask-patterned wet etching photolithography) are limited to approximately 100 µm, making them more suitable for larger diameter flow fields than PTL layers. Sintered titanium powder materials can achieve pore sizes ranging from 6 µm to 20 µm. However, sintered Ti powder PTLs are expensive to produce and have more random interstitial spaces that limit flow and reactivity at certain locations within the PTL. Furthermore, the porosity of the material is also limited by the diameter of the powder particles.

[0006] Accordingly, industry requires cheaper and more uniform materials to form the PTL layer of the electrolytic cell stack. Summary of the Invention

[0007] Ideally, a PTL should be composed of several layers of titanium material (foil or sheet), each layer having a uniform pore size and distribution, with the pore size decreasing sequentially in each layer, thereby creating a free and direct flow pattern between the flow field and the catalyst layer.

[0008] The PTL prepared according to the teachings of the present invention is composed of a micro-expanded Ti metal mesh layer, which can precisely control the thickness, porosity, tortuosity, pore size, interlayer connectivity and surface roughness of individual layers, while making the pore size distribution almost zero.

[0009] In particular, the present invention relates to the application and manufacture of an anode side element formed of multiple micro-expanded metal mesh layers, and further relates to an anode assembly comprising a novel micro-expanded PTL and combined flow field and bipolar.

[0010] This invention directly relates to the use of “micro-expanded” metal mesh PTL sub-assemblies (i.e., micro-expanded metal foil layers) having novel characteristics of pore size of 3 µm to 30 µm and porosity (mesh open area) of 10% to 50%; and further relates to methods for manufacturing expanded metal meshes and anode assembly assemblies.

[0011] The flow field layer may include expanded metal foils or sheets with relatively large pore sizes, 100 µm or larger, and manufactured using conventional metal expansion, wet etching lithography, laser or other suitable techniques.

[0012] In some embodiments, the bipolar plate, flow field layer, and porous transport layer are stacked and vacuum diffused into a single integrated assembly, thereby eliminating the need to coat each individual layer and improving the contact interface between each layer.

[0013] The outer edges of the combined stack are trimmed to the desired size for assembly with other components of the PEM stack. The anode assembly is also coated with platinum group conductive metals on the PTL side using a physical vapor deposition (PVD) coating method in a high-throughput coating production line, and with gold material coated on the bipolar plate side, coating only the outer surface, thereby reducing coating material costs and increasing production speed and efficiency.

[0014] The purpose of the anode assembly design and manufacturing method of the present invention is to improve the performance of the electrolyzer through better electrical contact between different layers, through a more uniform flow path of the flow field and PTL, and to reduce manufacturing costs by assembling the bipolar plate, flow field and PTL into a single integrated component.

[0015] While embodiments of the invention have been described with the features set forth, it should be understood that various combinations of these features are also covered by specific embodiments of the invention, and the scope of the invention is defined by the claims rather than the description. Attached Figure Description

[0016] Although the specification concludes with claims that specifically point out and explicitly claim protection for particular embodiments of the invention, different embodiments of the invention can be more readily understood and appreciated from the following description of different embodiments when read in conjunction with the accompanying drawings, in which: Figure 1 This is a schematic layer view of an exemplary PEM electrolytic cell cell stack; Figure 2 This is an illustration of an exemplary anode assembly according to the teachings of the present invention, which includes an anode bipolar plate, a multilayer porous flow field, and a multilayer porous anode transport layer constructed from multiple micro-expanded metal mesh layers. Figure 3 This is an illustration of an exemplary micro-expanded mesh PTL design formed by three separate micro-expanded Ti foils (separated on the left and combined on the right); Figure 4 This is an illustration of an exemplary metal mesh expansion process; Figure 5 This is a diagram of the micro-expansion device proposed according to the teachings of the present invention; Figure 6 These are illustrations of an exemplary PVD device according to the teaching content of the present invention; and Figure 7 This is a flowchart illustrating a method for manufacturing a complete anode assembly according to the teachings of the present invention. Detailed Implementation

[0017] Certain exemplary embodiments will now be described to provide a full understanding of the principles of the structure, function, manufacture, and use of the apparatuses and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. It will be understood by those skilled in the art that the apparatuses and methods specifically described herein and illustrated in the drawings are not limiting exemplary embodiments, and that the scope of the invention is defined only by the claims. Features illustrated or described in connection with one exemplary embodiment may be combined with features of other embodiments. Such modifications and variations are intended to be included within the scope of this disclosure. Furthermore, in this disclosure, similar numbered components of embodiments generally have similar features, and therefore each feature of each similar numbered component within a particular embodiment is not necessarily described in full detail. Additionally, with regard to the linear or circular dimension used in the description of the disclosed systems, apparatuses, and methods, such dimension is not intended to limit the types of shapes that can be used in conjunction with such systems, apparatuses, and methods. Those skilled in the art will recognize that equivalents of such linear and circular dimensions can be readily determined for any geometry. Furthermore, with regard to the directional terms used, such as top, bottom, up, or down, they are not intended to limit the systems, apparatuses, and methods disclosed herein. Those skilled in the art will recognize that these terms are used only in relation to the systems and apparatus under discussion and are not universal.

[0018] Now for reference Figure 2 and Figure 3 This disclosure provides information on anode assembly 10 ( Figure 2 The anode assembly includes bipolar plates 12, multilayer anode-side flow fields 14, and multilayer anode PTL 16. Figure 3 Layers 12, 14, and 16 are vacuum diffused together to form a single group 10, and PVD coated on their respective outer surfaces to form a fully integrated subassembly for direct assembly into the electrolyzer stack (see [link]). Figure 1 ).

[0019] Anode bipolar plates are conventional in the art and can comprise titanium plates with appropriate thickness and design for the intended stacked application. Other materials are also conceivable.

[0020] The multilayer anodic flow field may include multiple titanium metal layers with large porosity (up to 1 mm), but preferably 100 µm or larger. In some embodiments, the flow field porosity may be formed by expanding the metal layers, wet etching, laser drilling or other suitable techniques.

[0021] In some embodiments, the flow field may include one or more layers of material, but more preferably two to eight layers of material.

[0022] The multilayer PTL 16 may comprise a multilayer micro-expanded mesh titanium (Ti) foil. Individual layers may have different sheet thicknesses and pore sizes, as described below. The pore size may range from 3 µm to 30 µm (inclusive), and the expanded metal foil layer may have 10% to 50% of the mesh opening area. In some embodiments, three micro-expanded metal layers (16A, 16B, 16C) may be present, with their pore sizes gradually decreasing from the flow field side to the catalyst side (described further below).

[0023] The anode assembly of this invention integrates three technologies.

[0024] A) Micro-expanded metal mesh – Applying precision manufacturing techniques to the expansion metal manufacturing process allows for the production of micro-expanded porous meshes with pore sizes as follows. Optimized sizes typically range from 10 µm to 20 µm in pore diameter and >20% mesh open area. In some embodiments, a pore size of 10 µm is preferred, with a mesh open area or porosity >30%. These characteristics indicate that, relative to current expansion capabilities, pore size is reduced by at least 10 times and open area is increased by 3 times. The use of micro-expanded PTLs produces high-performance components that meet capital cost targets using scalable, zero-waste mechanical manufacturing methods. Manufacturing PTLs using micro-expanded meshes provides precise control over thickness, porosity, tortuosity, pore connectivity, and surface roughness, while achieving a near-zero pore size distribution. Due to unprecedented control over PTL characteristics, the optimized micro-expanded PTLs according to the invention meet current government-mandated performance targets and can be further optimized for operation in battery cells with low catalyst loadings. The invention aims to provide micro-expanded PTLs that meet 1.8 V battery cell performance at 3.0 A / cm² while achieving a cost of less than $39 / kW for anode assemblies with micro-expanded PTLs. The micro-expanded PTL design and method according to the invention also allows for optimization of PTL layers and electrolyzer configurations with lower catalyst loadings.

[0025] B) Diffusion bonding—The micro-expanded PTL layer and the expanded metal flow field layer are diffusely bonded to the bipolar plate, thereby producing the anode assembly 16 in a single bonding step. Figure 2In anode assembly manufacturing, diffusion bonding is implemented to improve the interface between the PTL, flow field, and bipolar plates by creating a permanent metallurgical bond between adjacent layers (explained further below). Through this improved bonding, anode assembly 16 exhibits improved durability without requiring the use of precious metal corrosion inhibitors within the anode assembly itself (i.e., no subsequent coating of each individual layer). The objectives of this invention include large-scale manufacturing at an annualized production capacity of 300 MW / year and a cost of less than $39 / kW, while simultaneously meeting durability requirements of 2.3 mV / khr at 3.0 A / cm² in a 3-cell stack.

[0026] C) Physical vapor deposition (PVD) coating – Diffusion-bonded anode assembly 16 is coated on the respective sides in a single pass via an online PVD coating system.

[0027] A) Micro-expanded Ti foil PTL The porous nature of expanded metal mesh makes it ideal for PTL applications. Metal expansion is a metal forming process, originally developed in 1884, in which a slit is made in a sheet of metal using a blade with a defined tooth pitch, and then the slit is opened into predictable, repeatable, and well-defined pores by stretching (see [link to PTL process]). Figure 4 ).

[0028] The metal mesh is then leveled using a series of rollers (not shown) to achieve a flat surface with the same material thickness as the original sheet. Expanded metals have a wide range of applications, such as structural components, energy-absorbing materials, filters, and electrodes for battery applications. Properties include high strength and stiffness, high quality efficiency, and high porosity. Expanded metals are highly economical because they are processed directly from sheet metal, resulting in virtually zero material waste. For this reason, in addition to the predictable and repeatable porosity of expanded metals, components utilizing metal foams, porous sintering agents, or woven metal wires are often replaced by expanded metal-based components where possible. In some existing PEM electrolyzer systems, conventional expanded metals with pore sizes up to 1 mm (1000 μm) have been used in three-dimensional flow fields, where several layers of expanded metal are stacked between bipolar plates and the PTL.

[0029] The primary purpose of the PTL (Porous Ligating Layer) located between the catalyst layer and the flow field at the top of the membrane is to provide electrical contact with the catalyst layer, remove heat, and allow mass transfer to and from the catalyst layer. Ideally, the PTL consists of a three-dimensional porous network within the metal matrix, which provides minimal resistance to fluid transport between the flow field and the catalyst layer while achieving tight electrical contact through the metal layer. This is crucial for advanced, low-load catalyst layers with poor in-plane conductivity. Design considerations were controlled by optimizing the transport of reactants to and from the catalyst layer, where the reaction occurs at the multiphase boundary between liquid water, gaseous products, the proton-conducting membrane / ionomer, the electron-conducting PTL, and the catalyst. Based on these considerations, the optimal average pore size of the PTL in contact with the catalyst layer was found to be in the range of 10 µm to 15 µm, with a porosity >20%. Although the ideal PTL shares many characteristics with the expanded metal flow field, existing expansion methods cannot produce such small pore sizes. Currently, standard expansion technology is limited to expansion inserts with pitch as low as 1 mm, step accuracy of approximately 100 µm, and stroke rate as high as 600 strokes per minute.

[0030] Mask patterning wet etching lithography can allow pore sizes as low as 100 µm, but as mentioned above, the optimal average pore size is still 10 times smaller (10 µm).

[0031] Fabricating meshes with the optimized PTL porosity requirements described above requires novel micro-expansion techniques and methods as disclosed herein. Generating 10 µm porosity requires micro-expansion inserts with a tooth pitch of up to 18 µm.

[0032] After each stroke, the expanding blade moves less than 10 µm laterally and downward on the wafer with an accuracy of <0.1 µm in each direction. Due to the small step size, more than 1500 strokes may be required to produce a 1 cm long mesh.

[0033] To achieve the 10 µm high precision requirement for the mesh, the micro-expander employs several precision control technologies and manufacturing methods, including: a) Femtosecond laser fabrication of carbide teeth for expanded cutting blades; b) Piezoelectric actuation of the expanding blade, c) Precision flexible bearings, d) Actively liquid cool the piezoelectric actuator housing to maintain the temperature below 1 degree Celsius, and e) Vibration damping of the base and frame, all of which are contained within a structure designed to withstand vibrations of more than 3,000 strokes per minute. Figure 5 The diagram illustrates the proposed configuration of the expander.

[0034] The expanding blade can produce 500 to 5000 teeth per inch, with a spacing of 5 μm to 50 μm between the teeth.

[0035] In an exemplary embodiment, a platinum foil with a thickness of 12.5 μm is passed through an expander to produce an expanded metal mesh material. Exemplary pore sizes can range from 3 μm to 30 μm, and the expanded metal foil layer can have a mesh opening area of ​​10% to 50%.

[0036] The expanded mesh produced by the micro-expander can be passed through a leveling machine (not shown) to ensure that the expanded mesh returns to the thickness of the initial foil without significant bending in the middle of the mesh. This can be achieved even with a mesh thickness of 12.5 μm using a commercial leveling machine. Furthermore, the roughness of the micro-expanded mesh is controlled by the roughness of the leveling rollers, which can achieve Ra roughness as low as 25 nm using commercial leveling rollers, far lower than the roughness (>1 µm) achievable through sintering PTL.

[0037] Generating a PTL 16 from a micro-expanded mesh requires stacking and diffusion-bonding multiple layers of expanded mesh. These layers can be generated from meshes with different pore sizes and orientations, with the general design principle being to ensure that each pore should have a flow path through the PTL. Because micro-expanders can produce uniform pores of relevant size and opening area, the micro-expanded mesh allows for precise control over the design and performance of the PTL. This control enables the PTL layers to seamlessly adapt to the large and growing body of research on optimal PTL characteristics, thus rapidly optimizing micro-expanded PTL systems.

[0038] Return to reference Figure 3 An exemplary embodiment of PTL 16 includes a 3-layer PTL design, which includes: 1) A 50 µm thick layer with 60 µm pores (16A). 2) A 25 µm thick layer (16B) with 30 µm pores, and 3) Layers (16C) with a thickness of 12.5 µm and a porosity of 15 µm are stacked in the anode group 10, wherein the layer 16A with the largest porosity is in close proximity to the flow field 14.

[0039] Figure 3 Both individual layers (16A, 16B, 16C) and the combined PTL stack (16) are depicted. An exploded view (left) and a combined view (right) illustrate a 540 µm x 540 µm cross section of the PTL 16, which consists of three layers of micro-expanded mesh. As described above, each layer has pore sizes of 15 µm, 30 µm, and 60 µm, such that for each 15 µm pore adjacent to the catalyst layer, there is a fluid path through the PTL.

[0040] Preliminary techno-economic modeling suggests that 3-layer micro-expanded PTLs can be manufactured at a lower cost than currently sintered Ti PTLs.

[0041] Compared to state-of-the-art sintered powder PTLs, micro-expanded PTL designs offer several compelling advantages, including: 1) Controllable porosity – adjustable up to 50% of the open pore area; 2) Fixed, controllable, hierarchical pore size – with an effective pore size distribution of 0 in each layer of the micro-expanded PTL; 3) Reduced layer thickness – sintered PTLs are typically 250 µm thick, while a 3-layer micro-expanded PTL will be 90 µm thick, with individually fabricated layers as thin as 13 µm; 4) Lower tortuosity – micro-expanded PTLs create near-straight-through fluid paths through planar surfaces, and the hierarchical porosity provides lateral pathways for bubble aggregation; and 5) Lower surface roughness – achieving Ra as low as 25 nm.

[0042] B) Diffusion binding A major drawback of the expanded metal flow field in PEM electrolytic cells is the high contact resistance generated between adjacent expanded mesh layers during operation. For titanium-based expanded meshes, this high contact resistance is attributed to the growth of a resistive layer of TiO2. Methods to prevent this increase in interfacial contact resistance are limited, and current practice involves platinum coating each individual mesh layer. Diffusion bonding (where adjacent mesh layers are metallurgically bonded to each other) eliminates the need for platinum coating of individual mesh layers. Diffusion bonding of titanium is carried out under high pressure (1 MPa to 10 MPa), high temperature (800°C to 1100°C), and high vacuum (<10⁻⁵ Torr). This requires a dedicated vacuum furnace and fixtures capable of applying the required pressure in situ.

[0043] Under these conditions, atoms diffuse into each other on adjacent mating surfaces of the workpiece to form an integral joint indistinguishable from the base material. Since the mating surfaces are now part of the material matrix, there is no longer a surface for TiO2 growth, thus eliminating the increase in interfacial contact resistance. Therefore, diffusion bonding can combine individual flow field layers together. Similarly, diffusion bonding can also combine individual PTL layers together as well as combine the outermost flow field layer to the PTL and bipolar plate. This invention implements the combination of all layers of PTL 16, flow field 14, and bipolar plate 12 to produce an integrated anode assembly 10 in a single step, thereby eliminating multiple process steps and minimizing process costs.

[0044] C) Physical vapor deposition (PVD) For the diffusion-bonded anode assembly 16, a noble metal (platinum group metal) coating is required only on the outer surface of each side of the assembly. Due to the high porosity of the anode assembly, standard electroplating deposition methods result in over-deposition of noble metals because it is difficult to limit deposition to the surface layer. PVD provides a significantly improved line-of-sight deposition method suitable for coating the surface of the anode assembly of the present invention.

[0045] PVD encompasses a large family of deposition methods, among which DC magnetron sputtering is one of the simplest and most economical coating methods for depositing thin metal layers. This technology is used for metallization of microelectronic circuits, the application of magnetic films in magnetic storage devices, optical storage films for CDs and DVDs, and decorative coatings for jewelry. Economical magnetron sputtering has been realized for the mass production of optical discs. A thin (<100 nm) aluminum coating is applied to these discs to create a reflective coating that allows laser systems to read the discs. Since the 1980s, this coating has been sputtered onto discs one at a time using in-line coating systems, with a coating rate of less than 2 seconds per disc. One challenge with these systems is the low target utilization (<50%) before the target needs to be replaced. To achieve cost-effectiveness, this material (composed of platinum group metal targets) is recycled and reused in new targets to restore the material's value.

[0046] Figure 6 The paper discloses an online PVD coating system in which the cycle time for each group is less than 5 minutes (including vacuum establishment and coating of multiple materials).

[0047] Figure 7 A flowchart illustrates a method for manufacturing a complete anode assembly according to the teachings of the present invention.

[0048] Therefore, it is understood that the present invention will provide a novel anode assembly comprising a porous transport layer (PTL) formed of multiple layers of micro-expanded metal mesh. This disclosure further provides a scalable production facility for manufacturing anode assemblies at a cost target of $39 / kW suitable for meeting a production cost target of $2 / kg H2. Furthermore, the development of the micro-expanded PTL will create the first economically competitive PTL to replace sintered powder and sintered fiber PTLs.

[0049] The specific objectives of this invention can be achieved through the following criteria.

[0050] 1. An electrolytic cell porous transport layer (PTL) comprising at least one micro-expanded titanium (Ti) foil, the at least one micro-expanded titanium (Ti) foil having a sheet thickness in the range of 10 µm to 45 µm, a pore size in the range of 3 µm to 30 µm, a pore density in the range of 10% to 50% and a surface roughness (Ra) of 25 nm or greater.

[0051] 2. An electrolytic cell PTL comprising a plurality of stacked micro-expanded Ti foils.

[0052] 3. An electrolytic cell PTL, wherein each of the plurality of stacked micro-expanded Ti foils has a gradually decreasing pore size from the outside to the inside.

[0053] 4. An electrolytic cell PTL, wherein each of the plurality of stacked micro-expanded Ti foils has a gradually decreasing thickness from the outside to the inside, and each of the plurality of stacked micro-expanded Ti foils has a gradually decreasing pore size from the outside to the inside.

[0054] 5. An electrolytic cell PTL comprising three stacked Ti foils, wherein the pore size of the inner foil is X, the pore size of the middle foil is about 2X, and the pore size of the outer foil is about 3X, thereby providing a fluid path through the PTL for each pore in the inner foil.

[0055] 6. An electrolytic cell anode assembly comprising: a bipolar plate; a porous flow field, wherein the porous flow field includes at least one layer of expanded metal mesh with a pore size of 100 µm or greater; and a porous transport layer (PTL) comprising at least one micro-expanded titanium (Ti) foil having a sheet thickness in the range of 13 µm to 45 µm, a pore size in the range of 3 µm to 30 µm, a pore density in the range of 10% to 50% and a surface roughness (Ra) of 25 nm or greater.

[0056] 7. An electrolytic cell anode assembly comprising a plurality of stacked micro-expanded Ti foils.

[0057] 8. An electrolytic cell anode assembly, wherein each of the plurality of stacked micro-expanded Ti foils has a gradually decreasing pore size from the outside to the inside.

[0058] 9. An electrolytic cell anode assembly, wherein each of the plurality of stacked micro-expanded Ti foils has a gradually decreasing thickness from the outside to the inside.

[0059] 10. An electrolytic cell anode assembly, wherein each of the plurality of stacked micro-expanded Ti foils has a gradually decreasing thickness from the outside to the inside.

[0060] 11. An electrolytic cell anode assembly, wherein each of the plurality of stacked micro-expanded Ti foils has a gradually decreasing thickness from the outside to the inside, and each of the plurality of stacked micro-expanded Ti foils has a gradually decreasing pore size from the outside to the inside.

[0061] 12. An electrolytic cell anode assembly comprising three stacked Ti foils, wherein the inner foil has a pore size of X, the middle foil has a pore size of approximately 2X, and the outer foil has a pore size of approximately 3X, thereby providing a fluid path through the PTL for each pore in the inner foil.

[0062] 13. An anode assembly for an electrolytic cell, comprising three stacked Ti foils, wherein the thickness of the inner foil is X, the thickness of the middle foil is approximately 2X, and the thickness of the outer foil is approximately 3X.

[0063] 14. An anode assembly for an electrolytic cell, wherein the bipolar plate, the porous flow field, and the PTL diffusion are combined to form an integrated anode assembly.

[0064] 15. An anode assembly for an electrolytic cell, wherein the outward-facing surface of the bipolar plate is coated with gold by PVD, and wherein the outward-facing surface of the PTL is coated with platinum by PVD.

[0065] Using diffusion bonding and PVD coating to manufacture anode assemblies offers new opportunities for high-volume, high-yield manufacturing, and integrates these technologies into a single-step diffusion bonding process and a single-pass multi-component PVD coating.

[0066] While certain specific structures embodying the invention have been shown and described herein, it will be apparent to those skilled in the art that various modifications and rearrangements of the components can be made without departing from the spirit and scope of the invention, and that the invention is not limited to the specific forms shown and described herein.

Claims

1. An electrolytic cell porous transport layer (PTL) comprising at least one micro-expanded titanium (Ti) foil, said at least one micro-expanded titanium (Ti) foil having a sheet thickness in the range of 10 µm to 45 µm, a pore size in the range of 3 µm to 30 µm, a pore density in the range of 10% to 50% and a surface roughness (Ra) of 25 nm or greater.

2. The electrolytic cell PTL as described in claim 1, comprising a plurality of stacked micro-expanded Ti foils.

3. The PTL electrolytic cell as described in claim 2, wherein, Each of the plurality of stacked micro-expanded Ti foils has a gradually decreasing pore size from the outside to the inside.

4. The PTL electrolytic cell as described in claim 2, wherein, Each of the plurality of stacked micro-expanded Ti foils has a gradually decreasing thickness from the outside to the inside.

5. The PTL electrolytic cell as described in claim 3, wherein, Each of the plurality of stacked micro-expanded Ti foils has a gradually decreasing thickness from the outside to the inside.

6. The PTL electrolytic cell as described in claim 3, comprising three stacked Ti foils, wherein, The inner sheet has a pore size of X, the middle sheet has a pore size of 2X, and the outer sheet has a pore size of 3X, thus there is a fluid path through the PTL for each pore in the inner sheet.

7. The PTL electrolytic cell as described in claim 5, comprising three stacked Ti foils, wherein, The inner sheet has a pore size of X, the middle sheet has a pore size of 2X, and the outer sheet has a pore size of 3X, thus there is a fluid path through the PTL for each pore in the inner sheet.

8. The PTL electrolytic cell as described in claim 4, comprising three stacked Ti foils, wherein, The thickness of the inner sheet is X, the thickness of the middle sheet is 2X, and the thickness of the outer sheet is 3X.

9. The PTL electrolytic cell as described in claim 5, comprising three stacked Ti foils, wherein, The thickness of the inner sheet is X, the thickness of the middle sheet is 2X, and the thickness of the outer sheet is 3X.

10. An anode assembly for an electrolytic cell, comprising: Bipolar plates; A porous flow field, wherein the porous flow field comprises at least one layer of expanded metal mesh with a pore size of 100 µm or larger; as well as A porous transport layer (PTL) comprising at least one micro-expanded titanium (Ti) foil having a thickness in the range of 13 µm to 45 µm, a pore size in the range of 3 µm to 30 µm, a pore density in the range of 10% to 50%, and a surface roughness (Ra) of 25 nm or greater.

11. The electrolytic cell anode assembly of claim 10, comprising a plurality of stacked micro-expanded Ti foils.

12. The electrolytic cell anode assembly as described in claim 11, wherein, Each of the plurality of stacked micro-expanded Ti foils has a gradually decreasing pore size from the outside to the inside.

13. The electrolytic cell anode assembly as described in claim 11, wherein, Each of the plurality of stacked micro-expanded Ti foils has a gradually decreasing thickness from the outside to the inside.

14. The electrolytic cell anode assembly as described in claim 12, wherein, Each of the plurality of stacked micro-expanded Ti foils has a gradually decreasing thickness from the outside to the inside.

15. The electrolytic cell anode assembly as described in claim 12, comprising three stacked Ti foils, wherein, The inner sheet has a pore size of X, the middle sheet has a pore size of 2X, and the outer sheet has a pore size of 3X, thus there is a fluid path through the PTL for each pore in the inner sheet.

16. The electrolytic cell anode assembly as described in claim 14, comprising three stacked Ti foils, wherein, The inner sheet has a pore size of X, the middle sheet has a pore size of 2X, and the outer sheet has a pore size of 3X, thus there is a fluid path through the PTL for each pore in the inner sheet.

17. The electrolytic cell anode assembly as described in claim 13, comprising three stacked Ti foils, wherein, The thickness of the inner sheet is X, the thickness of the middle sheet is 2X, and the thickness of the outer sheet is 3X.

18. The electrolytic cell anode assembly as described in claim 14, comprising five stacked Ti foils, wherein, The thickness of the inner sheet is X, the thickness of the middle sheet is 2X, and the thickness of the outer sheet is 3X.

19. The electrolytic cell anode assembly as described in claim 10, wherein, The bipolar plate, the porous flow field, and the PTL diffusion are combined to form an integrated anode assembly.

20. The electrolytic cell anode assembly as described in claim 10, wherein, The outward-facing surface of the bipolar plate is coated with gold by PVD, and the outward-facing surface of the PTL is coated with platinum by PVD.

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